(a) No landing fees shall be charged against aircraft when such aircraft is landing from a search-and¬rescue mission, a medical air evacuation or other emergency.

(b) Aircraft, after takeoff from an airport in American Samoa forced to return due to mechanical problems and/or weather conditions, will not be charged landing fees.

(c) Aircraft unable to depart due to mechanical difficulties or weather conditions will not be charged parking fees. It shall be the duty of the airport manager to determine whether or not such conditions or difficulties, as outlined in this subsection, exist.

(d) Locally based airline companies or air taxi services who lease ground space at the airport will not be charged any parking fees.

(e) Aircraft landing after a test or training flight shall be exempted from half the landing charges enumerated in 21.0201.

(f) Locally based airline companies or air taxi services shall be exempt from all landing fees after a test or training flight so long as no paying passengers are on board the aircraft at the time.

(g) The following categories of aircraft are exempt from all airport charges: